Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with optical components. For example, an electronic device may have an ambient light sensor, an optical proximity sensor, image sensors, light sources, and other optical components.
In an electronic device with a display, display border regions are often provided with opaque borders. The use of opaque borders helps hide internal components from view.
To accommodate optical component in the opaque border region of an electronic device display, optical component window regions may be formed in an opaque region such as an opaque display border region. In some arrangements, clear windows may be formed. Clear windows exhibit good light transmission, but are highly visible within the opaque display border region and can therefore be unsightly.
To help visually match the appearance of optical component windows to surrounding opaque border material, optical component windows can be formed from dark window coatings such as polymer layers containing dark dye or pigment. Dark window coatings may exhibit a dark outward appearance that matches nearby opaque border material while allowing light to pass through the window coating to accommodate an optical component.
The amount of light that is transmitted through an optical window with a dark window coating can be relatively small (e.g., 5%), which can adversely affect optical component performance. For example, light sensor noise may be higher than desired due to the relatively small amount of light that is transmitted. Although the light transmission level of a dark window coating could be increased to enhance sensor performance by thinning the dark window coating, this would make the window coating lighter in appearance and therefore less able to match the appearance of surrounding opaque border material.